Among the social institutions that promote nationalism, the three most important are:
a) schools, the family, and political parties.
b) the military, state religion, and athletics.
c) the family, athletics, and political parties.
d) schools, the military, and state religion.

The family is not very strong at promoting nationalism: for once, there can be family members of other nationalities, which would promote multinationalism! so we can reject a) and c)

now, military and state religion are both found in the other options and we have to choose between school and athletics - and school is more effective! so the correct answer is D.

Dis an orderly way to conduct research